1. Field of the Invention
The present invention relates to a cloud-probing apparatus.
The invention also relates to an atmospheric humidity profile or temperature profile or cloud height measuring apparatus.
2. Brief Description of the Prior Art
According to the prior art, semiconductor pulse lasers (pulsed diode lasers) are used for cloud probing. In these solutions, the laser's entire wavelength band is sent to the object being measured and the backscattered light is detected. In the detection of the backscattered signal, either completely separate detector optics is used, or alternatively partly the same optics has operated in both the transmission and in the detection.
A drawback in the prior art is that, despite its good properties, the method is sluggish, due to the non-ideal properties of the transmitting diode laser. The transmission power of a pulsed diode laser is spread over a wide wavelength range. At high transmission powers, a pulse laser also heats up, and heating causes the centre wavelength of the transmission power to shift. The manufacturing tolerance of the centre wavelength of a diode laser is also large. Due to the broad band and instability, the signal-noise ratio has been unsatisfactory.
In the prior art, test apparatuses are also used, in which the lasers operate in single mode. Such lasers are extremely expensive and, due to the single mode, the output takes place in a linear spectrum, which, in some measurement applications, is hypersensitive to the measuring variables or the properties of the atmosphere.